The effect of light exposure on the cleavage rate and implantation capacity of preimplantation murine embryos

•The implantation capacity and the immunomodulatory function of embryos exposed to white light for 25 min or 50 min is significantly reduced.•The harmful effect of white light was partly counteracted by the use of a red filter due to the increased wavelength, of the red light.•Based on these data, the use of red filtered light is advisable during embryo manipulation in IVF laboratories. During assisted reproduction the embryos are subjected to light. We investigated the relationship between light exposure and the developmental- and implantation capacity of mouse embryos. In vitro cultured embryos were exposed to white or red filtered light, then transferred to the uteri of pseudo-pregnant females. The mice were sacrificed on day 8.5 and implantation sites were counted. The number of nucleic acid containing (PI+) extracellular vesicles (EVs) in culture media of light-exposed and control embryos, as well as, the effect of the EVs on IL-10 production of CD8+ spleen cells was determined by flow cytometry. DNA fragmentation in control and light exposed embryos was detected in a TUNEL assay. The effect of light on the expression of apoptosis-related molecules was assessed in an apoptosis array. Light exposure significantly reduced the implantation capacity of the embryos. The harmful effect was related to the wavelength, rather than to the brightness of the light. Culture media of light exposed groups contained significantly higher number of PI + EVs than those of the control embryos, and failed to induce IL-10 production of spleen cells. The number of nuclei with fragmented DNA, was significantly higher in embryos treated with white light, than in the other two groups. In conclusion exposure to white light impairs the implantation potential of in vitro cultured mouse embryos. These effects are partly corrected by using a red filter. Since there is no information on the light sensitivity of human embryos, embryo manipulation during IVF and ICSI should be performed with caution.